Compact circular linkage for a pushing actuator

ABSTRACT

A compact unitized mechanical linkage, which can be handled as a single piece within a valve top works, transmits force and motion of a piezoelectric actuator stack to a moveable element in a control valve. The linkage has few parts and all may be made at low cost.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. § 119(e) to U.S.Provisional Application Ser. No. 62/589,062 filed Nov. 21, 2017, whichis incorporated by reference herein in its entirety for all purposes.This application is related to U.S. patent application Ser. No.15/182,978, titled “LOW HYSTERESIS DIAPHRAGM FOR A VALVE,” filed Jun.15, 2016 and U.S. Pat. No. 9,109,732B2, titled “EZ-SEAL GASKET FORJOINING FLUID PATHWAYS,” issued Aug. 18, 2015.

BACKGROUND

Embodiments of the present invention are related to a linkage for usewith an actuator that extends when activated. The linkage is compact andcircular in shape which makes it especially useful with bellows andpiezoelectric actuators. Embodiments of the invention are particularlyuseful in valves intended for proportional, or modulating, control offluid delivery within industrial processes making semiconductor devices,pharmaceuticals, or fine chemicals, and similar fluid delivery systems.

Using piezoelectric actuators in normally closed proportional valves forhigh purity fluid delivery in semiconductor capital equipment is known.Typical designs transmit actuator motion to the movable elements insidesuch valves through relatively complicated mechanisms comprised of manyseparate pieces which often are costly to make. Mechanical assemblieshaving more than a dozen individual parts are common and often involvecross drilling through cylindrical elements, several separate springsand pins, truncated or polygonal shapes, and so forth. For example, U.S.Pat. No. 8,181,932B2 issued to Matsumoto, et al., includes a disc-shapedfirst preload jig having two parallel chordal through-holes capturingcoupling pins which project through corresponding radial holes in atubular actuator box and a concentric second preload jig. Anotherexample, Japanese Patent No. 4119109 (discussed as prior art within U.S.Pat. No. 9,163,743 issued to Hidaka, et al.) includes a support cylindermade from Invar material having diametrically opposite arch-shapedradial openings which accommodate inserted hat-shaped semicircular splitbase pieces. Another example, U.S. Pat. No. 9,625,047B2 issued toHirose, et al, includes a lower support cylinder within which a supportframe is horizontally disposed through notches (in the support cylinderwalls) and threaded items are secured with locking screws havinghexagonal internal openings (typically made by broaching processes).

SUMMARY

In consideration of the foregoing applicant has invented a compactcircular linkage, for use with an expanding (pushing) actuator in anormally closed valve, which has a reduced number of easily made partsand can be handled as a single simple subassembly. An embodiment of amechanical linkage between an expanding actuator and a moveable elementof a valve comprises a thrust plate contacting a stationary portion ofthe valve, and a moveable hidden fork having two or more prongspenetrating axial thru-slots in the thrust plate, wherein the two ormore prongs are permanently attached to a lifting nut mechanicallyconnected to the moveable element. The expanding actuator may be apiezoelectric stack. The valve may be a proportional modulating valve.In some embodiments the hidden fork prongs are permanently attached bywelding. In some embodiments the thrust plate, hidden fork, and liftingnut are axisymmetric and of a circular shape. In some embodiments thethrust plate has a circumferential region with a radius to causeautomatic centering of the thrust plate when captured by a matingconical shape.

In one aspect of the present disclosure, a linkage assembly is providedto operatively couple an expanding valve actuator and a movable elementof a valve housing of a valve. In some embodiments, the linkage assemblycomprises a thrust plate, a lifting housing to engage the expandingvalve actuator, a ring nut, and a lifting element. The thrust plate hasa thrust plate body and includes a plurality of thru-slots defined inthe thrust plate body and that extend axially through the thrust platebody. The lifting housing includes a plurality of prongs depending fromthe lifting housing and extending through at least one of the pluralityof thru-slots. The ring nut is secured to the valve housing andsurrounds the plurality of prongs. The ring nut secures the thrust plateto the valve housing. The lifting element is secured to the plurality ofprongs and is securable to the movable element.

In some embodiments, the linkage assembly further comprises a guide discattached to the thrust plate body and attached to the lifting housing tocenter an upper end of the thrust plate body within the lifting housingand to provide angular indexing between the plurality of prongs and theplurality of thru-slots.

In some embodiments, the guide disc is attached to the thrust plate bodyby one of a weld, at least one threaded fastener, and at least onerivet, and the guide disc is attached to the lifting housing by at leastone of a weld, at least one threaded fastener, and at least one rivet.

In some embodiments, the guide disc is attached to the thrust plate bodyby at least one first rivet received in at least one first blind holedefined in the thrust plate body, and wherein the guide disc is attachedto the lifting housing by at least one second rivet received in at leastone second blind hole defined in the lifting housing.

In some embodiments, the lifting housing is cylindrical, and theplurality of prongs includes two arcuate prongs that are symmetricallyarranged on a lower end of the lifting housing, the two arcuate prongsbeing circumferentially spaced apart by two reliefs definedcircumferentially between the two arcuate prongs.

In some embodiments, the plurality of thru-slots includes two arcuatethru-slots that are symmetrically arranged on the thrust plate body, thearcuate thru-slots being separated by radial bridges of the thrust platebody.

In some embodiments, the thrust plate includes a reduced diameter upperbody portion connected to a full diameter lower body portion, the upperbody portion being connected to the lower body portion by the radialbridges.

In some embodiments, the thrust plate body includes a button centered onthe upper body portion of the thrust plate body, the button beingconfigured to contact the expanding valve actuator.

In some embodiments, the ring nut is externally threaded to engage amating female threaded counterbore of a valve housing to secure thethrust plate body to the valve housing.

In some embodiments, a conical surface of the ring nut mates with acircumferential region of the thrust plate, the circumferential regionhaving a shoulder radius to center the thrust plate within the valvehousing when the conical surface of the ring nut is tightened againstthe circumferential region of the thrust plate.

In some embodiments, the movable element is a control shaft of anormally closed diaphragm valve, the control shaft being secured to acontrol plate body that is configured to sealingly engage an orificeridge of the normally closed diaphragm valve, and wherein the liftingelement includes an internally threaded hole that screws onto thecontrol shaft.

In some embodiments, the linkage assembly further comprises a guide discattached to the thrust plate body and attached to the lifting housing tocenter an upper end of the thrust plate body within the lifting housingand to provide angular indexing between the plurality of prongs and theplurality of thru-slots, the guide disc being attached to the thrustplate body by at least one first rivet received in at least one firstblind hole defined in the thrust plate body being attached to thelifting housing by at least one second rivet received in at least onesecond blind hole defined in the lifting housing.

In some embodiments, the lifting element has a circular shape and has acircumferential step, each prong including a step relief at a lower endof the prong secured to the circumferential step of the lifting element.

In some embodiments, each of the lifting element, the thrust plate, thering nut, the lifting housing, and the guide disc are made from a metalmaterial or a polymer material.

In some embodiments, the movable element is a control shaft of anormally closed diaphragm valve, the control shaft being secured to acontrol plate body that is configured to sealingly engage an orificeridge of the normally closed diaphragm valve, and wherein the liftingelement includes an internally threaded hole that screws onto thecontrol shaft.

In some embodiments, the plurality of thru-slots includes at least twoarcuate thru-slots symmetrically arranged on the thrust plate body, thearcuate thru-slots being separated by radial bridges of the thrust platebody.

In some embodiments, the ring nut is externally threaded to engage amating female threaded counterbore of a valve housing to secure thethrust plate body to the valve housing.

In some embodiments, the lifting element has a circular shape and has acircumferential step, each prong including a step relief at a lower endof the prong secured to the circumferential step of the lifting element.

In some embodiments, the expanding valve actuator is one of apiezoelectric stack, a bellows, and a pneumatic piston.

In some embodiments, the valve is a proportional modulating valve.

In some embodiments, the valve is a normally closed valve.

In some embodiments, the plurality of prongs are permanently attached tothe lifting element.

In some embodiments, the plurality of prongs are permanently attached tothe lifting element by welding.

In some embodiments, the thrust plate, the plurality of prongs, and thelifting element are axisymmetric and of a circular shape.

In some embodiments, a conical surface of the ring nut mates with acircumferential region of the thrust plate, the circumferential regionhaving a shoulder radius, to center the thrust plate within the valvehousing.

In some embodiments, a linkage assembly according to any of the aboveembodiments is provided in combination with the valve housing, the valvehousing including a counterbore to receive the linkage assembly. In someembodiments, the linkage assembly further comprises a low hysteresisdiaphragm formed within the valve housing. In some embodiments, thelinkage assembly further comprises a control shaft secured to the lowhysteresis diaphragm and a control plate body secured to a lower end ofthe control shaft. In some embodiments, the linkage assembly includes aboost spring seated in the counterbore beneath the linkage assembly, theboost spring providing one of actuator preload or extra shut-off force.

In another aspect of the present disclosure, a linkage is providedbetween an expanding valve actuator and a movable element of a valvehousing of a valve. The linkage comprises a fixed portion configured toattach to the valve housing and a movable portion configured for axialmovement relative to the fixed portion. The fixed portion includes athrust plate including a plurality of thru-slots; and a ring nutsecuring the thrust plate to the valve housing. The movable portionincludes a lifting housing engaging the expanding valve actuator, and alifting element. The lifting housing includes a plurality of prongs. Theplurality of prongs are surrounded by the ring nut. Each one of theplurality of prongs extends through a respective one of the plurality ofthru-slots. The lifting element is secured to the plurality of prongs ofthe lifting housing, and the lifting element is securable to the movableelement.

In some embodiments, the valve is a normally closed valve, and theexpanding valve actuator is one of a piezoelectric stack, a bellows, anda pneumatic piston.

In some embodiments, the valve is a normally closed valve.

In some embodiments, the plurality of prongs are permanently attached tothe lifting element.

In some embodiments, the plurality of prongs are permanently attached tothe lifting element by welding.

In some embodiments, a conical surface of the ring nut mates with acircumferential region of the thrust plate, the circumferential regionhaving a shoulder radius.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an exploded view of an embodiment of a circular linkage inaccordance with aspects of the present invention;

FIG. 2A is a perspective of the circular linkage of FIG. 1 with aquarter segment removed to reveal the relationship of assembled parts;

FIG. 2B is a cross-sectional view of the circular linkage of FIG. 1taken along plane I-I as indicated in FIG. 2A showing a lifting elementpositioned below a thrust plate;

FIG. 2C is a cross-sectional view of the circular linkage of FIG. 1taken along plane II-II as indicated in FIG. 2A showing weld attachmentof a lifting element to lifting housing hidden fork prongs;

FIG. 3A is an exploded of a representative valve using the circularlinkage of FIG. 1 with a piezoelectric actuator;

FIG. 3B is a cross-sectional view of the representative valve of FIG. 3Ataken along plane III-III as indicated in FIG. 3A;

FIG. 3C is a cross-sectional view of the representative valve of FIG. 3Ataken along the plane IV-IV as indicated in FIG. 3A;

FIG. 4 is an exploded view of another embodiment of the circularlinkage;

FIG. 5 is an exploded view of another embodiment of the circularlinkage; and

FIG. 6 is an exploded view of another embodiment of the circularlinkage.

DETAILED DESCRIPTION

This invention is not limited in its application to the details ofconstruction and the arrangement of components set forth in thefollowing description or illustrated in the drawings. The invention iscapable of other embodiments and of being practiced or of being carriedout in various ways. Also, the phrasing and terminology used herein isfor the purpose of description and should not be regarded as limiting.The use of “including,” “comprising,” or “having,” “containing,”“involving,” and variations thereof herein, is meant to encompass theitems listed thereafter and equivalents thereof as well as additionalitems. The use of directional adjectives “inner, “outer,” “upper,”“lower,” and like terms, are meant to assist with understanding relativerelationships among design elements and should not be construed asmeaning an absolute direction in space nor regarded as limiting.

The small number of pieces needed to make a representative example of anembodiment of the compact circular linkage 100 for a pushing actuator isshown by the perspective exploded view illustrated in FIG. 1. There arefive major pieces: a lifting element 10, a thrust plate 30, a ring nut50, a lifting housing 70, and a guide disc 90. These pieces fit togethermaking the compact circular linkage 100 a subassembly suited to easy usein the top works of an exemplary valve 300 as illustrated in FIG. 3A.The relationship of the circular linkage subassembly pieces will befurther explained with reference to the cross-sectional viewsillustrated in FIG. 2A-2C. A representative use of the circular linkage100 in a valve top works can be appreciated by considering an exemplaryvalve 300 using the present inventor's U.S. patent application Ser. No.15/182,978, titled “LOW HYSTERESIS DIAPHRAGM FOR A VALVE,” filed Jun.15, 2016, now U.S. Pat. No. 10,113,665, as illustrated in FIG. 3A, FIG.3B, and FIG. 3C herein. The low hysteresis diaphragm is formed within avalve housing 360 to which a top works is assembled. The valve housing360 may be sealing joined to a valve body 364 by using a metallic seal365. In the present illustrations FIG. 3A, FIG. 3B, and FIG. 3C, themetallic seal 365 is made according to the present inventor's U.S. Pat.No. 9,109,732B2, titled “EZ-SEAL GASKET FOR JOINING FLUID PATHWAYS,”issued Aug. 18, 2015. Additional parts of the complete valve 300 includea piezoelectric actuator stack 369 contained within an actuator housing368, having an associated locking nut 367, which mates to the circularlinkage 100 as further shown in FIG. 3B and FIG. 3C. An optional boostspring 366 may be included to provide actuator preload or extra shut-offforce.

The bottom central element of the compact circular linkage 100 is thelifting element 10 which makes connection with a moveable element in theexemplary valve 300. As used in the illustrated exemplary valve 300, thelifting element 10 has an internally threaded hole 12 and screws onto acontrol shaft 362 within the typical low hysteresis diaphragm valvehousing 360. The outer periphery of the lifting element 10 has anoptional recess 11 which provides alignment and serves as a weldpreparation feature when the lifting element 10 is joined to a lowerportion of the lifting housing 70 as further described in thisdisclosure. A lifting element 10 may be easily made as a circular shapemanufactured by a screw machine, or lathe for example, and the optionalrecess 11 then formed as a simple circumferential step.

The next element of the compact circular linkage 100 immediately abovethe lifting element 10 is the thrust plate 30 which has a lower portionof full diameter larger than the lifting element 10, and an upperportion of reduced diameter smaller than the lifting element 10. Theradially outermost region 31 of the transition from full diameter toreduced diameter is provided with a shoulder radius to be contacted bythe ring nut 50. Inward of the radiused region 31 are four sectorscomprising a first radial bridge 35, an arcuate first axial thru-slot32, a second radial bridge 37, and an arcuate second axial thru-slot 34.The reduced diameter upper portion is connected to the full diameterlower portion by the two radial bridges 35,37. An actuator contact 39,typically a hemispherical button shape, surmounts the reduced diameterupper portion and is centered on the axis of the thrust plate 30. A pairof axial blind holes 36,38 are located diametrically opposite theactuator contact 39. The circular shaped thrust plate 30 may also beeasily manufactured by a screw machine or lathe.

The next element of the compact circular linkage 100, immediately abovethe lower portion of the thrust plate 30, is the ring nut 50. The ringnut 50 is a full diameter ring of relatively short axial length, andintermediate internal diameter, having an external thread which engagesa mating female threaded counterbore of the valve housing 360 used inthe exemplary valve 300. The lower inner diameter of the ring nut 50 maypreferably include a conical chamfer 51 for contacting the radiusedregion 31 of the full diameter portion of the thrust plate 30. Carefulconsideration of the mating between the valve housing 360 and thecircular linkage 100, as illustrated in FIG. 3B and FIG. 3C, furtherreveals how the conical chamfer 51 pushing against the thrust plateradius region 31 effects a natural centering of the thrust plate 30within the valve housing 360. This centering action minimizes undesiredbending forces which might otherwise be impressed upon the exemplarycontrol shaft 362. The ring nut 50 is, of course, a part typicallymanufactured by a screw machine or lathe.

The next element of the compact circular linkage 100, above the ring nut50, is the full diameter upper portion of the lifting housing 70. Thelifting housing 70 has a central bore through which the upper reduceddiameter portion of the thrust plate 30 may project enabling theactuator contact 39 to engage a piezo stack 369 as further described.The lifting housing 70 additionally has an intermediate diameter lowerportion which projects downward through the ring nut 50 and engages thearcuate axial thru-slots 32,34 in the full diameter portion of thethrust plate 30. The intermediate diameter portion of the liftinghousing 70 appears as a circular shell which has two diametricallyopposed portions removed to form reliefs 75,76 that leave two prongs72,74 of a hidden fork depending from the lifting housing 70 andprojecting through the arcuate thru-slots 32,34. The reliefs 75,76straddle the radial bridges 35,37 which are circumferentially adjacentthe arcuate thru-slots 32,34. The bottom ends of the hidden fork prongs72,74 have step reliefs 71,73 designed to engage the weld preparationfeature recess 11 of the lifting element 10. The four elements (liftingelement 10, thrust plate 30, ring nut 50, lifting housing 70) may becaptured together as a single subassembly by stacking those elements insequence and then attaching the bottom ends 71,73 of the hidden forkprongs 72,74 to the lifting element recess 11. The lifting housing 70and lifting element 10 should be joined together by a process whichmakes the two elements behave as a single piece so pushing and pullingaction of the lifting housing 70 is communicated directly to the liftingelement 10 without mechanical lash nor hysteresis. Laser welding,precision TIG welding, or electron beam welding are typical suitableprocesses. Brazing, adhesive bonding, radial locking pins, threadedfasteners, and other designs may also be feasible in some situations. Aninterference fit, snap action mating shapes, adhesive, or other designmethods may be considered for connecting the lifting element 10 to theexemplary control shaft 362, since pushing on the lifting housing 70will directly move the lifting element 10, but the internally threadedhole 12 is easiest to implement. As is the case with other previouslydescribed elements of the compact circular linkage 100, the liftinghousing 70 may be easily manufactured by a screw machine or a lathe.

The fifth and topmost element of the compact circular linkage 100 is theguide disc 90 which has two primary functions. The guide disc 90provides axial alignment of the reduced diameter upper portion of thethrust plate 30 by centering it within the central bore of the liftinghousing 70. The guide disc 90 also provides angular indexing between thelifting housing 70 and the thrust plate 30 to position the two prongs72,74 of the hidden fork projecting through the arcuate thru-slots 32,34so there is no rubbing nor other axial motion interference. The guidedisc 90 is a part easily flexible in a general axial direction butrelatively stiff in radial and circumferential angular location. Theguide disc 90 may be conveniently attached to the lifting housing 70 andthrust plate 30 by interference fit rivets 91,93,95,97 pushed intosuitable corresponding outer blind holes 77,78 of the lifting housingand inner blind holes 36,38 of the thrust plate. Other assembly methodssuch as welding or threaded fasteners may be considered, but the rivets91,93,95,97 benefit from relative ease of assembly when located abovelifting housing features (e.g. hidden fork prongs 72,74) that resist theforce of rivet insertion. The guide disc 90 may be made by chemicaletching of sheet metal stock, but it should also be appreciated all fiveelements 10,30,50,70,90 may also be manufactured of either metal orpolymer materials by processes such as injection molding, die-casting,or additive manufacturing methods such as 3D printing. In variousembodiments, one or more of the elements 10, 30, 50, 70, 90 may beformed from a corrosion resistant metallic alloy, such as type 316stainless steel, a nickel-based superalloy, a cobalt-based superalloy, anickel-chromium alloy, or a cobalt-chromium alloy, although othersuitable materials may be used, depending on the type of fluid. In someembodiments, one or more of the elements 10, 30, 50, 70, 90 may beformed from an alloy selected from Hastelloy® brand nickel-chromiumalloys available from Haynes International, or formed from an alloyselected from Elgiloy® brand cobalt-chromium alloys available fromElgiloy Specialty Metals. In some embodiments, one or more of theelements 10, 30, 50, 70, 90 may be formed from a polymer material, suchas a thermoplastic.

As illustrated in FIG. 3A, FIG. 3B, and FIG. 3C, the exemplary valve 300comprises a valve body 364 to which a valve housing 360 is sealingattached by threaded fasteners that compress an EZ-Seal gasket 365. Thecompact circular linkage 100 sits in a counterbore in the valve housing360. A typical assembly sequence would be to fit an optional boostspring 366 into the counterbore followed by the circular linkage 100.Then rotate the lifting housing 70, of the circular linkage 100, tothread the attached lifting element 10 onto the correspondingly threadedcontrol shaft 362 until the thrust plate 30 rests against thecounterbore bottom. The ring nut 50 may then be separately screwed intoa mating thread of the valve housing 360 counterbore so the conicalchamfer 51 pushes against the radiused region 31 of the thrust plate 30thereby centering and locking it inside the counterbore along with theboost spring 366. Adjustment shims and similar loose pieces are notneeded. A typical actuator housing 368 will screw into the full diameterportion of the lifting housing 70 causing a piezoelectric actuator stack369 to rest against the centered actuator contact 39 of the thrust plate30. The actuator housing may be locked into place by a locking nut 367as illustrated.

Operation of the exemplary valve 300 using the compact circular linkage100 is straightforward. An activation voltage applied to thepiezoelectric actuator stack 369 will cause the stack to expand inlength (extend). The lower end of the actuator stack 369 rests againstthe actuator contact 39, itself being part of the thrust plate 30 whichis in solid contact with the valve housing 360, and therefore the lowerend of the actuator stack 369 cannot move relative to the valve housing360. The upper end of the actuator stack 369 is in contact with theactuator housing 368 which must respond to the actuator stack expansionby rising upward together. The actuator housing 368 being threaded intothe full diameter portion of the lifting housing 70 makes the entirelifting housing 70 also rise upward, including the hidden fork prongs72,74 connected to the lifting element 10. In this manner the liftingelement 10 must rise and thereby lift the control shaft 362 which causesthe moveable control element to allow fluid flow through the valve body364.

The valve housing 360 includes a valve diaphragm 361 that may beintegrally formed with the valve housing 360. In some embodiments, thevalve diaphragm 361 is a low hysteresis valve diaphragm. In someembodiments, the movable element is a control shaft 362 that is affixedto the diaphragm. The moveable element may be comprised of a controlplate affixed to the control shaft that is affixed to the diaphragm. Thelifting element 10 includes an internally threaded hole that screws ontothe control shaft. FIGS. 3B and 3C show a normally closed valve in whicha control plate 363 is secured to a lower end of the control shaft 362.The control plate 363 has a control plate body that has a lower surface370 that sealingly engages an orifice ridge 371 of the normally closeddiaphragm valve. Due to the operation of the linkage 100 describedherein, expansion of the expandable actuator 369 causes upward movementof the actuator housing 368 relative to the valve housing 360, resultingin upward movement of the lower surface 370 of the control plate 363with respect to the orifice ridge 371.

Other shape combinations of hidden fork prongs and arcuate axialthru-slots may be considered by skilled designers. Another combinationis illustrated in FIG. 4 showing an exploded view of a compact circularlinkage 400 having a hidden fork structure comprising threesymmetrically placed axial members 472,474,476 which pass through threecorresponding axial thru-slots 432,434,436 in the full diameter portionof a thrust plate 430. Corresponding reliefs 473,475,477 between thehidden fork prongs 472,474,476 which straddle the radial bridges433,435,437 between the thru-slots 432,434,436 are shown along withsimilar features like numbered as in FIG. 1. One notable differencebetween the circular linkage 100 of FIG. 1 and the circular linkage 400of FIG. 4 is the changes in securing the guide disc 490. With thethree-way symmetry of the circular linkage 400 in FIG. 4 a designer maychoose three-way symmetry for the guide disc 490. Such an arrangementuses three inner rivets 487,488,489 which connect to the thrust plate430 and three outer rivets 481,482,483 that connect to the liftinghousing 470. This design choice benefits from the axial strength ofhidden fork prongs 472,474,476 to resist the insertion force whenplacing the outer rivets 481,482,483 securing the guide disc 490 via itsouter holes 491,492,493.

Yet another combination is illustrated in FIG. 5 showing an explodedview of a compact circular linkage 500 having a hidden fork structurecomprising four symmetrically placed axial members 572,574,576,578.Corresponding axial thru-slots 532,534,536,538 in the full diameterportion of a thrust plate 530, reliefs 575,577, etc. between hidden forkprongs 572,574,576,578, and straddled radial bridges 533,535,537, etc.between the thru-slots 532,534,536,538, are shown with similar featureslike numbered as in FIG. 1. This circular linkage 500 being bilaterallysymmetric only needs four rivets 591,593,595,597 securing the guide disc590 as in the original case 100 illustrated in FIG. 1. A designer mightalso choose to use round rods in an intermediate diameter arrayprojecting from a lifting housing passing through round holes, insteadof arcuate thru-slots, in a mating thrust plate but such an arrangementis likely more expensive to make than the screw machine oriented partsdescribed in this disclosure.

Another combination is illustrated in FIG. 6 showing an exploded view ofa compact circular linkage 600 having a hidden fork structure comprisingthree symmetrically placed axial members 672,674,676 which pass throughthree corresponding axial thru-slots 632,634,636 in the full diameterportion of a thrust plate 630. Corresponding reliefs 673,675,677 betweenthe hidden fork prongs 672,674,676 which straddle the radial bridges633,635,637 between the thru-slots 632,634,636 are shown along withsimilar features like numbered as in FIG. 1. Similar to the topmostelement of the compact circular linkage 100, the guide disc 690 providesaxial alignment of the reduced diameter upper portion of the thrustplate 630 by centering it within the central bore of the lifting housing670. The guide disc 690 also provides angular indexing between thelifting housing 670 and the thrust plate 630 to position the threeprongs 672,674,676 of the hidden fork projecting through three arcuatethru-slots 632,634,636 so there is no rubbing nor other axial motioninterference. The guide disc 690 is a part easily flexible in a generalaxial direction but relatively stiff in radial and circumferentialangular location. The guide disc 690 may be conveniently attached to thelifting housing 670 and thrust plate 360 by interference fit rivets691,693,695,697 pushed into suitable corresponding outer blind holes(not visible) of the lifting housing and inner blind holes 638,640 ofthe thrust plate. Other assembly methods such as welding or threadedfasteners may be considered, but the rivets 691,693,695,697 benefit fromrelative ease of assembly. The guide disc 690 may be made by chemicaletching of sheet metal stock, but it should also be appreciated all fiveelements 610,630,650,670,690 may also be manufactured of either metal orpolymer materials by processes such as injection molding, die-casting,or additive manufacturing methods such as 3D printing. Designers willalso appreciate welding of the lifting element 610 to the ends of thethree hidden fork prongs 672,674,676 may be done along an edge 611without need for a weld preparation type of recess shown in FIG. 1.Electron beam, laser, or similar welding processes are well suited tomaking this assembly.

Having thus described several aspects of at least one embodiment of thisinvention, it is to be appreciated various alterations, modifications,and improvements will readily occur to those skilled in the art. Suchalterations, modifications, and improvements are intended to be part ofthis disclosure, and are intended to be within the scope of theinvention. Accordingly, the foregoing description and drawings are byway of example only.

The invention claimed is:
 1. A linkage assembly configured to operatively couple an expanding valve actuator and a movable element of a valve housing of a valve, the linkage assembly comprising: a thrust plate having a thrust plate body and including a plurality of thru-slots defined in the thrust plate body and that extend axially through the thrust plate body; a lifting housing to engage the expanding valve actuator, the lifting housing including a plurality of prongs depending from the lifting housing and extending through at least one of the plurality of thru-slots; a ring nut secured to the valve housing and surrounding the plurality of prongs, the ring nut securing the thrust plate to the valve housing; and a lifting element secured to the plurality of prongs, the lifting element securable to the movable element.
 2. The linkage assembly of claim 1, further comprising a guide disc attached to the thrust plate body and attached to the lifting housing to center an upper end of the thrust plate body within the lifting housing and to provide angular indexing between the plurality of prongs and the plurality of thru-slots.
 3. The linkage assembly of claim 2, wherein the guide disc is attached to the thrust plate body by one of a first weld, at least one first threaded fastener, and at least one first rivet, and the guide disc is attached to the lifting housing by at least one of a second weld, at least one second threaded fastener, and at least one second rivet.
 4. The linkage assembly of claim 2, wherein the guide disc is attached to the thrust plate body by at least one first rivet received in at least one first blind hole defined in the thrust plate body, and wherein the guide disc is attached to the lifting housing by at least one second rivet received in at least one second blind hole defined in the lifting housing.
 5. The linkage assembly of claim 1, wherein the lifting housing is cylindrical, and the plurality of prongs includes two arcuate prongs that are symmetrically arranged on a lower end of the lifting housing, the two arcuate prongs being circumferentially spaced apart by two reliefs defined circumferentially between the two arcuate prongs.
 6. The linkage assembly of claim 5, wherein the plurality of thru-slots includes two arcuate thru-slots that are symmetrically arranged in the thrust plate body, the arcuate thru-slots being separated by radial bridges of the thrust plate body.
 7. The linkage assembly of claim 6, wherein the thrust plate includes a reduced diameter upper body portion connected to a full diameter lower body portion, the upper body portion being connected to the lower body portion by the radial bridges.
 8. The linkage assembly of claim 7, wherein the thrust plate body includes a button centered on the upper body portion of the thrust plate body.
 9. The linkage assembly of claim 8, wherein the ring nut is externally threaded.
 10. The linkage assembly of claim 9, wherein a conical surface of the ring nut mates with a circumferential region of the thrust plate, the circumferential region having a shoulder radius.
 11. The linkage assembly of claim 10, wherein the lifting element includes an internally threaded hole.
 12. The linkage assembly of claim 11, further comprising a guide disc attached to the thrust plate body and attached to the lifting housing to center an upper end of the thrust plate body within the lifting housing and to provide angular indexing between the plurality of prongs and the plurality of thru-slots, the guide disc being attached to the thrust plate body by at least one first rivet received in at least one first blind hole defined in the thrust plate body, the guide disc being attached to the lifting housing by at least one second rivet received in at least one second blind hole defined in the lifting housing.
 13. The linkage assembly of claim 12, wherein the lifting element has a circular shape and has a circumferential step, each prong including a step relief at a lower end of the prong secured to the circumferential step of the lifting element.
 14. The linkage assembly of claim 13, wherein each of the lifting element, the thrust plate, the ring nut, the lifting housing, and the guide disc are made from a metal material or a polymer material.
 15. The linkage assembly of claim 1, in combination with the valve housing of the valve, wherein the movable element is a control shaft of the valve, the control shaft being secured to a control plate body that is configured to sealingly engage an orifice ridge of the valve, and wherein the lifting element includes an internally threaded hole that screws onto the control shaft.
 16. The linkage assembly of claim 1, wherein the plurality of thru-slots includes at least two arcuate thru-slots symmetrically arranged on the thrust plate body, the arcuate thru-slots being separated by radial bridges of the thrust plate body.
 17. The linkage assembly of claim 1, wherein the ring nut is externally threaded.
 18. The linkage assembly of claim 1, wherein the lifting element has a circular shape and has a circumferential step, each prong including a step relief at a lower end of the prong secured to the circumferential step of the lifting element.
 19. The linkage assembly of claim 1, in combination with the valve actuator and the moveable element of the valve housing of the valve, wherein the expanding valve actuator is one of a piezoelectric stack, a bellows, and a pneumatic piston.
 20. The linkage assembly of claim 1, in combination with the valve housing of the valve, wherein the valve is a proportional modulating valve.
 21. The linkage assembly of claim 1, in combination with the valve housing of the valve, wherein the valve is a normally closed valve.
 22. The linkage assembly of claim 1, wherein the plurality of prongs are permanently attached to the lifting element.
 23. The linkage assembly of claim 22, wherein the plurality of prongs are permanently attached to the lifting element by welding.
 24. The linkage assembly of claim 22, wherein the thrust plate, the plurality of prongs, and the lifting element are axisymmetric and of a circular shape.
 25. The linkage assembly of claim 1, wherein a conical surface of the ring nut mates with a circumferential region of the thrust plate, the circumferential region having a shoulder radius.
 26. The linkage assembly of claim 1, in combination with the valve housing of the valve, the valve housing including a counterbore to receive the linkage assembly.
 27. The linkage assembly of claim 26, further comprising a low hysteresis diaphragm formed within the valve housing.
 28. The linkage assembly of claim 27, further comprising a control shaft secured to the low hysteresis diaphragm and a control plate body secured to a lower end of the control shaft.
 29. The linkage assembly of claim 26, further comprising a boost spring seated in the counterbore beneath the linkage assembly, the boost spring providing one of an actuator preload or an extra shut-off force. 